Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.
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Garmin Fenix 6 pro solar mainly because it tracks all my other metrics off the job and I use it for running, biking and swimming. It's pretty durable and has a wrist hr monitor in it It's fairly accurate too. The chest strap hrm is much more accurate though and what I wear when working out with activities off duty.
I had a Fenix 6 Pro Solar that recently bit the dust. I balked at the price of a similarly equipped Fenix 8 so bought an Epix 47 instead. Turns out I hated having an amoled screen. So I returned the Epix and bought an Instinct 3 with MIP. It’s a 45mm which I like so far.
I’ve used a Fenix 6 Pro Solar for ages and love it. Works awesome for MTB, running, road biking, and even mountaineering if that’s your jam. Only complaint is how I occasionally have trouble maintaining a solid synch connection with my phone. Happens rarely and is resolved by updating both phone and watch then repairing. Performance of the watch for tracking and providing live data is absolutely stellar. Just adjust the data collection settings to more often.
It wasn't ideal, but on my last event run of ~50hrs I used a smaller battery brick to recharge it while I ran after ~36hrs in. I put it in one of my water bottle pockets on my vest for about an hour, so I lost HR but kept GPS and the event tracking during the recharge. I have a Fenix 6 Pro Solar and yeah, better and newer watches exist now for longevity, but this was cheaper and got the job done.
I’ve had the Garmin Tactix Delta, Fénix 5x, 6 pro solar, 6x, 7x, and 8. I still go back and use my AU2 for a week from time to time. lol
Garmin Fēnix 6 Pro. I bought it second hand earlier this year. Cost nearly nothing and does everything I could want it to do and much more.
That and the super long battery life of a solar model for trekking.
Same. I wanted a Fēnix for hiking and a cheap second hand 6 was what I could afford at the time. Now that I can afford a later model I can't justify it to myself.
Garmin
Forerunner 255 Series
Long battery; but wrist HR tracking is inconsistent.

Garmin
Forerunner 955 Series
Best value, clear MIP screen; limited smartwatch features.

Garmin
Fenix 7 Series
Durable, multi-week battery, flashlight; high price, buggy software.
Garmin
Instinct 2 Series
Rugged, solar multi-week battery; bulky, small screen readability issues.

Garmin
Enduro 3
Multi-week solar battery, lightweight; but bulky form factor.

Ranked #1
Oura - Oura Ring Series

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Apple - Ultra Series

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Garmin - Enduro 3

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Garmin - Fenix 7 Series

Ranked #1
Garmin - Forerunner 255 Series

Ranked #1
Oura - Oura Ring Series